The present invention provides an image display system that displays a calibration image, then measures that calibration image and corrects the image signal accordingly, in order to reproduce a target color (such as a color that conforms to a ruleset such as sRGB) in a manner that conforms to the environment used in practice.
In a method that could be considered, by way of example, the image display system displays and measures calibration images for each predetermined grayscale in each of the red (R), green (G), blue (B), and white (W) colors.
However, this method takes a lot of time for the image display system to measure the colors and generate correction data (such as a one-dimensional look-up table) for correcting the image signal, and the quantity of correction data is also large.
One method of reducing the quantity of this correction data is disclosed in Japanese Patent Application Laid-Open No. 10-271352, by way of example, which refers to a method of performing gamma correction on pattern data for color correction by switching among a plurality of gamma conversion curves.
However, this document does not address the technical problem of increasing speed. That is because the application of this document is the representation of colors as subtractive colors in devices such as scanner, and it does not refer to devices that represent colors as additive colors, with is a prerequisite for image display.
In other words, factors such as ambient light have an effect on additive colors, which affects the reproduced colors.
In situations such as a presentation at a client's location, in particular, it is necessary for the presenter to set up the projector at that site and immediately display images that are suited to the environment in which the projector is used.
Since factors such as of ambient light change a reproduced image appearance, it is necessary for the image display system to perform grayscale correction.
However, a phenomenon called deteriorated tone-mapping of highlight details occurs if the output grayscale values are too high, whereas a phenomenon called deteriorated tone-mapping of shadow details occurs if the output grayscale values are too low, so it is necessary for the image display system to perform the grayscale correction in an appropriate manner.